Variable pitch sheave indicators



Nov. 8, 1955 D. FIRTH 2,722,842

VARIABLE PITCH SHEAVE INDICATORS 6 Sheets-Sheet l Filed Aug. 14, 195s IN V EN TOR.

Nov. 8, 1955 D. FIRTH VARIABLE FITCH SHEAVE INDICATORS 6 Sheets-Sheet 2 Filed Aug. 14, 1955 Nov. 8, 1955 Filed Aug. 14, 1955 D. FIRTH VARIABLE FITCH SHEAVE INDICATORS 6 Sheets-Sheet 5 INVENTOR.

yal/dj TZ/ff BY Nov. 8, 1955 D. FIRTH 2,722,842

VARIABLE PITCH SHEAVE INDICATORS Filed Aug. 14, 1953 6 Sheets-Sheet 4 INVENTOR.

Nov. 8, 1955 D. FlR'rH 2,722,842

VARIABLE PITCH SHEAVE INDICATORS Filed Aug. 14, 1953 6 Sheets-Sheet 5 1N VEN TOR.

Nov. 8, 1955 D. FIRTH 2,722,842

VARIABLE FITCH SHEAVE INDICATORS Filed Aug. 14, 1953 v e sheets-sheet e d 1N IEN TOR. 9 g I@ ywwff@ United States Patent Hee ka', Ind., a corporation The operating] diameter e .verideie pitch v-beit sheet/e isnt-.pendent npdn the pnsitinn therein et -the vbeit dt beits iised tiierevvith. Adjustment et the sita-.eve to contract the sfpa'eing between onfronting sheave discs or flanges will eausethe bl't or belts to nieve outwardly ir1 the sheave, arlddjust'rentto eXpaid 'sucl i spacing vvill ease the b elt o r belts to 'move inwardly, a's is well understood in the art.

The general objee't of 'the present invention is to provide, in e veritiere pi'teii v -peit siiedve; priest-teenies ineens for iridica'tiiigbel't positions therein t dijferent adjusted positions of the slife'av'e discs or flanges, wherebyto facilitate preei'se setting or adjustment ef the sheave to obtain desired operating diameter.

The ir'nf/entiori is 'pplieable tobo'th single groove and mltifgiooved sheaves, and is not intended to be limited to any speiie sheave strt're,

An iiinstis'tive siieeve fen e fwn-beit drive, hayingthe invention eppiied -tiieietd in diie prece-eene rotin; is shown in Figs. lto 6 of 4the eeoinpnying Havviigsl- Fig. 1 a Afront erid elevation of s'id illtstrative sheave, portions of the sheave discs `or rges being broken away.

Fig. 2 is a longitudinal seetioii of said szlteav taken on the line 2-2 of `Fig. 1, theslieave hub being shovvn in elevation; This gire sliows" the shear/e ontraeted for driving et eire'ctive din'ietei', the V-eeitsbei'n'g held byponfronting discs in their outermost position in tbe sheve. t `Eig.' 3 is a longitudinal Half s'eetiii shovt/ing the sheave Aexpanded for driving at iiiinnru'rn effec ve dia'iiietei," the ts beingA in the innermost position' which they can ssuine in 'the shi-Leve; d

gitiidinis'eeiidn teken dii tiiepent line 4 j-fi f Ei"g; i; inking iii tiie d iieet'ion di tiijjeeridws, outer portions of the' sheve Harige's being broken away.

Figs.' 5 itjd 6, 'tireiv en sedie t'wie tiitef the precedin'g' gres, are views of the indieating means of the iiiiistitiv'e shetive, Fig. r5 being' en enierged fr dgfiient ef Fi'g: 2, atiiirigg. ,s big an en'd eig-,vatten f tiie central portion if the sliev'e, lkiiig t the indito'r end thereof.

Figs 7 en 'd s are view eiiespondiiig te Figs. 5 end 6 siinviiig e iiiediiied fiin n'fiiidieeting ineen-js.

Figi 9 i`s` 'a view Corresponding to Fig. 5 of another form 'of iiidieatiii'g` ieiis.

Fig. 10 is a de elopriient on aflat surface of the gradted spiral line and iiid,1' 'ci al shovitii on' hub in FigL 9. Figs, 1I arid 12' ie vievvs corresponding to Fig'. 5 of other niddiea'tioii's.

Fig. 13 is al vivv eorrespiding to Fig; 5 sljvviiig iridicating means simil'r' to that of Figs. 5 and 6 with a'n ancillary feature.' i

Fig. 1`4 is a development on a at surface of the spiral line onthe liub of. Fig'. 13.4

. Fig.' 15 is a mutilated end View .of Fig. 13 .shovving a portion of the dial thereon, which dial is identical to that of fig. 6.

Fig. 16 is ingit'id'iiti seetin i single g'e sheave having the invention applied thereto, the sheave discs being shown in position for driving at maximum effective diameter.

Fig. 17 is a half 1section of `vsaid single 'groove sheave adjusted for 'driving atmiriirum effective diameter.

Fig. 18 is anenla'rged fragment of Figi. 13.

Fig. 19 is an enlarged end elevation of the central portion of said single groove sheave, looking at the indicatbrend thereof.

Referring toFigs. l to 6, the tvvo-belt sheave therein shown for illustration comprises 4a series of annular discs 11, 12, 13 and '14 ca'rried by and in driving connection with a hub 15 on whieh thedises are mounted with capacity for a'xial movement relative to each other and to the hub. In' this instance the dises are slidably tted on a cylindriol hub `t Wliieh they are splined by the key 16. The hub i `s shown Yais @bored hub to b e fitted on and keyed to a shaft and held lfrom 'Xil displacement by set screws 17. r lhe 'sheave dis'esor flanges are arranged to provide grooves for the V-belts 18",' one of which belts is engaged by the eetifiii'ting 4dises iiend 12 nd the other by the con f roriting dises 1 3 and '1 `he non-adjacent dises A11 and 1 3 engaging eor'r'e's'ponding 'sides of the belts are rigidly connected in spa'ed relation for axial movemerit as a unit, as are also t li`e opposing discs 12 and 14. The spacing rid eoiirieetin'g means shown comprise tiebolts o r srews 20 eone'c'tig'jhe dises 11 and 13 and interposed tubular spers y21 slidable in theintervening disc 12, 'and tie-bolts or screws 2 2 eonnecting the alternatediscs I2 n'd 14a'n`d interposed tubular spacers 23 slidable in' the intervening dise 13. lfhespa'eing of the discs of the reepetive Vshiftble inits or groups of rigidly connected discs issuch as to permitshifting them simultaneously equal distanes iii opposite directions between the positions siiwn in Figs'. 2 and 3. Titus the illustrative sheave is of the typeeinpris'in'g tvvo intera'rrang'ed and oppositely axially sliftible gr'dp's of dises eooperating' to the belt grooves, being of s iniilrb'ody oonstrution to that of the Firth Pate'it No. 2,400,294 of May 14, 1946.

The adjusting means of tlie illustrative sheave of a type and enns'triietidn dis-` ed in depending eppiica- Serial No. 277,638, tiled tion f or a'djiistble" 'sli' March 20, 1952; not# 1 ent Number 2,697,947. Said adjustingrnens 'corriprises a` differential sfcrewv25 arranged beside arid parallel With the hub, in the surrounding edjnsteeie sheeye bndy. the seievv has e coarse threaded portion 26 eXtri'diii"g' through and in threaded engagement with intermediate dise `12, and e ne threaded eritension 27 engagedby a non-rotatable nut 2 8 ixed position on the 'sheave hub. The dise 13 is recessed 29 to on'tain s aid t Wl-ien the sheave discs are in the re'ltidrisliip vvn iii Fig, 3. The coarse and fine tiiieeds nf tiife edjs'ting s'revv @ingress in [the seine dire'ctinii, the s'ei'ew isiiigeitiier right handed er left hnded with res et to' ig'oth threads, Dii'e tn the dinerenc iii pitch of said threads; thesc'revv when turned vvili nieve' tite dise iii einen it is threaded in direction n'ppdsite te that tv iiieii tite seievy nieves exiauy'. Tiie dise i4 being rigidly connected with said disc 12 ivill riiove axially therev'vith.' The' ends o f the serev'? biitt a'gais't the discs 11 and I3; 'so that a'iiil thrust of the sc'revi/ in either direction is. against a dis'c adjacent to the intermediate one iii which the screw is threaded. The dises 11. and 13 being rigidlyeonn'ected vvill rrive as unit` axially vvith theserew. The head ofvthe screw,.rot2itably fitted in a smooth-bored recess 30 in the end d isc,1v1has al wrench socket 31 accessible: to a wrench through a hole 32 in said enfitdisa, ThePithbist1i-sqat$e thread. .O f the Screw is piefrably twice thetiafihemee thread. ,fherepf- Hence by. Ustensiles eslfswtheseroiin oripiireliiypf discs 11 and 13 and the group or plurality of alternate discs 12 and M can be shifted simultaneously equal distances in opposite directions, thereby changing the pitch diameter o-f the sheave without shifting the centers of the belt grooves, and obtaining a relatively large range of adjustment for a comparatively short travel of the screw.

indicating means provided by the present invention is utilized in the illustrative sheave to indicate pitch diameters thereof at different adjusted positio-ns of the sheave discs. The invention with respect to the indicating means may be embodied in dilferent specific forms. The specific indicating means shown in Figs. 5 and 6 will. be irst described.

One of the end discs of the illustrative sheave, preferably the disc 14, is referred to as the indicator disc. it being a part of the indicating means. The inner edge of the back side of said disc, referred to as the gauge edge, defines a circle enclosing and contiguous to the cylindrical surface of the hub 15. The plane of said gauge edge is referred to as the gauge plane. In this instance, the gauge plane is that of the face of an annular dial plate 36 which is fixed to the back of the indicator disc 14tand may be regarded as a part of said disc. When said disc is in the maximum pitch position shown in Fig. 2, the gauge plane coincides with the plane indicated by the dotted line A-A in Fig. 5, and when said disc is in the minimum pitch position shown in Fig. 3 the gauge plane coincides with that indicated by the dotted line B-B in Fig. 5. The distance between A-A and B-B is that which the indicator disc travels as it is shifted axially from one of its extreme positions to the other.

Scribed on the hub 15 is a spiral line 37 arranged to be progressively intersected by the gauge plane as it shifts with the disc ld between its two extreme positions. In this instance the spiral line goes completely around the hub and connects points 40 and 4l in the planes A-A and B-B, both of which points lie in the same longitudinal line.

The dial plate 36 has on its face a dial or annular scale graduated by radiating division lines or marks contiguous to the edge 35, as shown for example in Fig. 6. The dial graduations and accompanying indicia are preferably etched on the dial plate. Use of an etched dial plate iixed to the indicator disc, rather than a dial inscribed on the back of said disc, is advantageous for convenience and economy in manufacture.

What may be termed the zero mark of the dial, designated in Fig. 6 by the reference numeral 42 (and shown therein with accompanying dial numbers l0 and 5.5)7 registers with the point 41 in the plane B--B of Fig. 5 when the indicator disc 14 is in its minimum pitch position. and with the point 4t! in the plane A--A when said disc is in its maximum pitch position. The dial plate 36 is fastened to the indicator disc by screws 43 passing through arcuate slots in said plate, to permit adjusting the angular position of the dial on the indicator disc for accurate registration of the zero mark with the points 4l) and lll in the two extreme positions of the indicator disc.

As the indicator disc moves from either extreme position to the other, the gauge edge 35 thereof continually crosses the spiral line 37 on the hub, wherefore the graduation lines or marks on the dial successively meet or register with said spiral line. These marks with the aid of appropriate indicia on the dial indicate pitch diameters at the respective adjusted positions of the sheave discs at which said marks respectively register with said spiral line. Hence when the sheave is adjusted by turning the adjusting screw 25 in either direction, the operating pitch diameter thereof as adjusted will be indicated by the dial mark in registry with said spiral line, or indicated approximately by the dial mark nearest to coincidence with said spiral line.

The maximum and minimum pitch diameters being known, the pitch diameters at the positions of the sheave disc at which the dial marks respectively meet said spiral line can be easily ascertained without separate measuring or use of ordinary gauges. If the indicator disc 14 moves a part of the distance between its two extreme positions, it will cause a proportionate increase or decrease in the pitch diameter. For example, if the indicator disc moves a quarter of said distance from minimum pitch diameter position, the resultant pitch diameter will be equal to the minimum plus one fourth of the difference between the maximum and minimum pitch diameters. Hence, by dividing the dial into as many equal divisions as the number of equal units of measure into which the said difference between maximum and minimum pitch diameters can be divided, the pitch diameters denoted by the dial marks can be easily computed.

The illustrative sheave, which in the application drawings (as distinguished from the patent drawings) is shown half size in Figs. l to 4 and full size in Figs. 5 and 6, is designed for varying the pitch diameter from a minimum of tive and a half inches to a maximum of ten inches. Thus the difference between maximum and minimum pitch diameters is four and a half inches, which equals forty-five tenths of an inch. Hence the dial is divided -into forty-live equal divisions, representing tenths of inches. The individual dial marks are shown in association with indicia of the corresponding pitch diameters, though if preferred such indicia may be provided only for the dial marks denoting inches and half-inches.

The dial may be of any appropriate design to suit requirements for any particular embodiment of the invention. The dial shown in Fig. 6 is graduated to denote pitch diameters in inches and tenths thereof. Because of restricted space for indicia, the large dial figures 6, 7, 8 and 9 and the dial numeral 10 are applied to dial marks or division lines denoting inches of pitch diameter, while the intervening graduations denoting tenths of inches are designated by small dial figures. Reading the dial in a clockwise direction, the dial numeral 5.5 is followed by small dial figures 6, 7, 8 and 9, denoting pitch diameters of 5.6 to 5.9. The next dial figure 6, relatively large, is followed by small dial ligures 1 to 9, denoting pitch diameters of 6.1 to 6.9". And so on around the dial to the dial numeral 10, which is applied to the same dial mark as the dial numeral 5.5.

Figs. 7 to l2 of the drawings show the indicator end portions of variable pitch sheaves similar to that hereinbefore described except for modifications of the indicating means.

Referring to Figs. 7 and 8, the spiral line 137, corresponding to but slightly greater in pitch than 37, connects points and 141 in the planes A-A and B-B, which points are somewhat angularly spaced or on different longitudinal lines. In this instance the spiral line 137 or its operative length does not go completely around the hub. The angular space occupied by the dial on the dial plate 136 is correspondingly less than 360. The dial is shown having main division lines with accompanying indicia of inches and half-inches of pitch diameter, and intervening divisions corresponding to quarters and eighths of inches. When the sheave discs are in minimum pitch position, the iirst or zero dial mark, designated by the dial numeral 5.5, registers with the point 141, and when the discs are in maximum pitch position the last dial mark l0 registers with the point 140. The operation is the same as that of the indicating means rst described. As the indicator disc 14 moves from either extreme position to the other, the dial marks are successively registered with the spiral line 137, and the pitch diameter of the sheave at any adjusted position of the sheave discs will be indicated by the dial mark in registry with or most nearly coincident with said spiral line.

Fig. 9 discloses a species of the invention having an indicating dial engraved on the sheave hub adjacent to -the spiral line thereon. Here the spiral line 237, connecting points in the planes A-A and B--B, is itself graduated by dial lines or marks with associated indicia of pitch diameters. A development on a flat surface of /f Said Spiral lie and associate-s1 dit-tis` .shewain s. .0l Sidspra1,1i1.1e 231 is. ShQWn as identical.. in nit1 1...a-.d angular extent to. 37 in Fis-. 5, ,though that is. hutxemv 91am. .It Willbe understood thatas thesheavediscs are shiftedfromcither,extreme position to the other, the sans@ plane f. fhaindiator disc 1,4., whichv` in thiS..,i11 stanceis the lplane of the back 4surface of psaidkdisc, shifts froml Afl-Ay to B-B or vice versa, andsuccessively lregisters with the points where the dial. marks meet the spiral line 2.37. In other words, vthe dialgrnarks successively register with successive points of intersectionpfsaid `spiral, line by the gauge plane. The pitchwdiameter ofmthe sheave at any adjusted position of the sheave discsjs indi,- calte'dby the dial mark coinciding or mostnearly `in coincidence with the gauge edge23l5V of the indicator disc.

.i Fig. 11 shows a modiication ,wherein theindicator disc designated by the numeral 4314, is formed on its back Side With. @Central conical protrusion 3,36.on.which the itsdivision lines radiating fromthegauge edge y3,35`4` The plane of said edge is the gauge plane, which in one extreme position of the sheave d iscs coincides with A-A and in the other extreme position coincides withB-B.

' Thus the indicating means of Fig. 1l isv the same'asin Figs.

l indicating dial (only partially shown) `is 4engraved with n ated byV the numeral 414, is formed ,on its back side withV a `central extension 436 having-acylindrical surface adjacent to the back surfaceof .the belt-engagingjportmion of said disc and a conicalsurface extendingfro'm said cylindrical surface to thegauge edge 4,35.V InV thisinstance the dial marks or division lines ,radiate vfrom said gaugeedg 435 on said conical surface and-extend onto said cylindrical surface where they are associated with indicia of the pitch diarri'ters'.

Referring to .rigs--1.3, 14- an; 15:. the .device therein illustrated is substantially the same G ,cp't that in Figs. 13, 14 andl hated Jby -the" numeral 537; is gr l fier as in Figs; 9 and 1o; by div extending longitudinally thereof from said spiral line, the hub being extended beyond the point 41 to allow room on the hub for said lines. Thus the device of Figs. 13, 14 and 15 combines the indicating means of Figs. 5 and 6 with the feature of a graduated spiral line on the hub, preferably omitting indicia on the hub. In operation, the graduation marks on the dial plate 36 will register successively with said spiral line at the points from which the division lines on the hub meet said spiral line. This may be of advantage to assist in easy and accurate reading of the dial.

The embodiment of the invention shown in Figs. 13, 14 and 15 includes two annular series of graduation marks or division lines, one being on the dial and the other on the hub, these series being correlated for the purpose stated in the preceding paragraph hereof. In this case, indicia of pitch diameters may be associated with either series of graduation marks.

Referring to Figs. 16 to 19, the single groove sheave therein shown comprises a pair of confronting discs 51 and 52 engaging an interposed V-belt 53, said discs being slidably fitted on and spliued to the hub 50. The means shown for adjusting the sheave is of a type and construction disclosed in my copending application Serial No. 277,639, filed March 20, 1952, now Patent No. 2,718,155, dated September 20, 1955. In this instance the discs are connected by a differential screw 55 swiveled to 51 and threaded in 52, said screw having a coarse-threaded portion 56 screwed into 52 and a fine-threaded extension 57 engaged by a non-rotatable nut 58 in iixed position on the hub. The coarse and tine threads of the screw progress in the same direction, the pitch of the coarse thread being twice that of the fine thread. By turning the screw,

Le time ,--.1f, inf. .t ,v vu-.4 R.' i. the discs can be shifted simultaneously equaldistances illopposite 4directions between the positions shown in FisSf16and17.-.. .1

l, ,Means for swivelingothe adjusting screw 55 to they disc 51 is shown, onan enlarged scalepin Fig. 18. As shown, the cylindrical head 60 ofthevscrew is rotatably fitted in ,aA recess therefor in said disc, which recess is open at itsfront end andnextends part way through the disc to a portion thereof providing the shoulder 61.A The last mentioned portion of said disc is apertured for passage of the. screw shank looselyl therethrough.V j The screw head 6 0jis held in abutting relation to the shoulder 61 by a washer 62 which is held in abutting relation to the screw headlby a snap ring 63 sprungsinto an annular groove in `the wall of said recess. The screw head is provided with a wrench Asocket 65 for engagement by a wrench for operating the screw.

, Thedisc 52 isy formed to house thenut 58 and so much of the adjusting screw as extendsrearwardly from the.'screw hole .therefor in said disc. As shown, said nut and portion of the screw are contained in a recess 66 in a rearward extension of the central portion of said disc, said extension forming an annular boss 67 to which i'sixed a dial plate 70 for coa'ction with the spiral line 71 on the sheave hb.

Any indicating means hereinbefore described as applied, to a pluralbelt sheave may b'e utilized in a single groove sheave. The indicating m'eans shown for example in the' sheave f Figs. 16 to' 19 is in accordance with the species of the invention shown in Figs. 5 and 6. In this instance the disc 52 is utilized as the indicator disc, the gauge' plane thereof being that o'f the dial on the etched dial plate 70. As Vthe sheave dises are shifted from maximumio minimum pitch position or vice versa; the gauge edge172,' sh`ifting from one to the other o'f the planes A-A and B'-B, continuallyfcrosses the Aspiral line 71 and registers successively with the dial marks on 70. The pitch dimter ofthe sheave at any adjusted position of the discs is indicated by the dial mark. in .registry or nearest in registry t said spiral line. It will be' understood that the', dial marks and indicia should beapp'ropriate to the dinerence between maximum and minimum pitch diame- Vters For example; if .the difference between such diarneters of the sheave of Figs. 16 to 19 is the same as in the two-belt sheaves previously described, the dial on the etched plate and the spiral line 71 may be identical t0 those of Figs. 5 and 6, and are so shown as identical, only for example.

In the several embodiments of the invention herein de` scribed, the dial marks are utilized with appropriate indicia to indicate pitch diameters. The same dial marks could be used with other appropriate indicia to indicate corresponding radial distances or twice such distances from the sheave axis to either the inner or outer surface of the sheave belt or belts. The positions assumed by the belt or belts in the sheave at different adjusted positions of the sheave discs may be indicated either by ir.- dicating the corresponding pitch diameters or by indicating the corresponding radial distances above mentioned or twice such distances. Expressions in the appended claims as to indicating belt positions are intended to be construed accordingly.

Notice is given that plural belt and single belt sheaves having the respective adjusting means herein described embody inventions respectively described and claimed in my said applications Serial Nos. 277,638 and 277,639.

I claim:

1. A variable pitch V-belt sheave comprising opposing bek-engaging discs, a cylindrical hub on which said discs are mounted for adjustability of their relative positions, screw means connected to said hub and discs for adjustably positioning the discs relative to the hub and to each other, and means including a spiral line on the hub and a gauge edge of one of said discs for indicating belt positions in the sheave at different adjusted positions of the discs.

2. A variable pitch V-belt sheave comprising opposing belt-engaging discs, a cylindrical hub on which said discs are mounted for adjustability of their relative positions, screw means connected to said hub and discs for adjustably positioning the discs relative to the hub and to each other, one of said discs being an indicator disc slidably fitted on said hub and movable axially in the adjusting operation, said indicator disc having an exposed back side the inner edge of which constitutes a gauge edge contiguous to the hub, a spiral line on the hub arranged to be continually crossed by said gauge edge as said indicator disc is shifted, and a dial on said indicator disc comprising graduation marks contiguous to said gauge edge for successive registry with said spiral line to indicate belt positions in the sheave at different adjusted positions of said discs.

3. A variable pitch tl-belt sheave according to claim 2 wherein the dial is divided into as many equal divisions as the number of equal fractions of a standard unit of measure into which the difference between the maximum and minimum pitch diameters of the sheave can be divided.

4. A variable pitch V-belt sheave according to claim 2 wherein the dial is provided by an etched plate aixed to the back side of the indicator disc.

5. A variable pitch V-belt sheave according to claim 2 wherein the indicator disc has on its back side a central conical extension and said dial is on said back side and graduated by division lines radiating from said gauge edge on the conical surface of said extension.

6. A variable pitch V-belt sheave according to claim 2 wherein the indicator disc has on its back side a central extension with a cylindrical surface adjacent to said back side and a conical surface extending from said cylindrical surface to said gauge edge, the dial being on said extension and graduated by division lines radiating from said gauge edge on said conical surface and leading to indicia on said cylindrical surface.

in a variable pitch V-belt sheave, an indicator disc movable axially in the operation of adjusting the pitch diameter, a cylindrical hub on which said disc is slidably fitted, a spiral line on said hub arranged to be continually intersected by the plane of the inner edge of the back side of said disc as it is shifted, and a dial on said disc having graduation marks contiguous to said edge for successive registry with successive points of intersection of said spiral line by said plane for indicating belt positions in the sheave at different positions of said disc.

8. A variable pitch V-belt sheave comprising opposing belt-engaging discs, a cylindrical hub on which said discs are mounted for adjustability of their relative positions, screw means connected to said hub and discs for adjustably positioning the discs relative to the hub and to each other, one of said discs being an indicator disc slidably fitted on said hub and movable axially in the adjusting operation, said indicator disc having an exposed back side the inner edge of which constitutes a gauge edge contiguous to the hub, a spiral line on the hub arranged to be continually crossed by said gauge edge as said indicator disc is shifted, and a dial on the hub comprising graduation marks contiguous to said spiral line for successive registry with said gauge edge to indicate belt positions in the sheave at different adjusted positions of said discs.

9. A variable pitch V-belt sheave according to claim 8 wherein the dial is divided into as many equal divisions as the number of equal fractions of a standard unit of measure into which the difference between the maximum and minimum pitch diameters of lthe sheave can be divided.

l0. In a variable pitch V-belt sheave, an indicator disc movable axially in the operation of adjusting the pitch diameter, a cylindrical hub on which said disc is slidably fitted, a spiral line on said hub arranged to be continually interesected by the plane of the inner edge of the back side of said disc as it is shifted, and a dial on said hub having graduation marks contiguous to said spiral line for successive registry with said edge to indicate belt positions in the sheave at different positions of said disc.

References Cited in the file of this patent UNITED STATES PATENTS 

